According to a new numerical model of biogeochemistry and climate, developed by researchers at the Georgia Institute of Technology, Earth will maintain its oxygen-rich atmosphere for a billion years, before rapid deoxygenation makes the atmosphere reminiscent of early Earth.
The study, published in Nature, has important ramifications not only for the future of Earth's biosphere, but also for the search for life on Earth-like planets.
Stochastic approach
Oxygen (and the photochemical byproduct, ozone) is the most accepted biosignature for the search for life on exoplanets, and, from the looks of it, the oxygen-rich atmosphere might only be possible during 20-30% of the entire history of Earth as an inhabited planet.
The atmosphere after the major deoxygenation is characterized by high methane, low levels of CO2, and no ozone layer. The Earth system will likely be a world of anaerobic life forms.
Given that the modeling of the future evolution of the Earth harbors many uncertainties in the geological and biological evolutions, for the modeling of the future evolution of the Earth adopted a stochastic approach, which allows researchers to obtain a probabilistic assessment of the lifetime of an oxygenated atmosphere.
As explained Kazumi Ozaki, assistant professor at Toho University and lead author of the research:
For many years, the lifespan of Earth's biosphere has been debated based on scientific knowledge about the sun's constant brightness and the global carbonate-silicate geochemical cycle. One of the corollaries of such a theoretical framework is a continued decline in atmospheric CO2 levels and global warming on geological time scales. In fact, it is generally thought that Earth's biosphere will come to an end within the next 2 billion years due to a combination of overheating and a shortage of CO2 for photosynthesis. If true, it can be expected that atmospheric O2 levels will also eventually decrease in the distant future. However, it is unclear exactly when and how this will occur.
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Future lifespan of Earth's oxygen-rich atmosphere is about 1 billion years
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